The 3rd Generation Partnership Project (3GPP) is a collaboration between groups of telecommunications associations, to make a globally applicable third generation (3G) mobile phone system specification within the scope of the International Mobile Telecommunications-2000 project of the International Telecommunication Union (ITU). FIG. 1 illustrates a 3GPP architecture for multiple access in a non-roaming scenario, and FIG. 2 illustrates a 3GPP architecture for multiple access in a roaming scenario. The architectures depicted in FIGS. 1 and 2 show the scenarios in which a client-based mobility protocol S2c—i.e., DSMIPv6 (Dual stack Mobile IPv6)—is used for connectivity and mobility between 3GPP accesses and non-3GPP accesses. S2c is described in more detail in 3GPP TS 23.402 V8.3.0 and 3GPP TS 23.401 V8.3.0, which are incorporated herein by reference. The mechanisms specified in 3GPP TS 23.402 can be used to connect a user equipment (UE) (or mobile terminal) in parallel to an evolved packet core (EPC) via a 3GPP access network and a non-3GPP access network towards different packet data networks (PDNs).
Currently, the 3GPP specifications listed above—3GPP TS 23.402 V8.3.0 and 3GPP TS 23.401 V8.3.0—do not specify how a UE can simultaneously access a network through multiple heterogeneous accesses. However, the mechanisms specified in the specifications listed above can be used to connect a UE in parallel (via different PDNs) to an EPC via 3GPP access network and a non-3GPP access network.